Familiar to all are the various bar codes and magnetic strips employed by businesses to perform identification functions and the various devices used to read them. Generally, magnetic strips are read by swiping a card with the strip on it, such as a credit card, through a reader. Magnetic strips can also read by contact or proximity devices where the card, such as a parking or access card, is placed on or held close to the reader. Bar codes are generally read by using a “light gun” to read the code and identify the item associated with that particular code. Bar codes and magnetic strips are presently the identification systems of choice because they are cheap.
The applications for which bar codes and magnetic strips are useful is limited, however, by the relatively small amount of data they can encode and by their inherent readability limitations. One such readability limitation is the range at which they can be read. Both are short range systems that require the reader to contact or be very close (a few centimeters, at most) to the bar code or magnetic strip in order to decode data. They are also limited by the fact that no obstruction can exist between the reader and the bar code or magnetic strip for the reader to accurately decode data. The orientation of the reader relative to the bar code or magnetic strip can also impose a significant readability problem. If the reading device is not properly aligned or is held at an incorrect angle, the encoded information can not be read. Because of these problems, each individual read operation requires manual scanning by a human operator if high read accuracy is needed. The various limitations of bar codes and magnetic strips have prevented their use in a wide range of applications for machine readable tags that need highly reliable and totally automated reading at read ranges up to several meters.
The radio frequency identification (“RFID”) tag is another prior art type of identification device. When interrogated, RFID tags reflect or retransmit a radio frequency signal to return an encoded identification number to the interrogator. A good example of RFID tags is their usage in the collection of highway and bridge tolls where an RFID tag is positioned on a user's vehicle to respond to an interrogation signal when the vehicle passes through a toll collection point. A reading device connected to a computer processes the tag identification number and uses the decoded information to charge the toll to the user's credit card.
Prior art RFID tag devices are of two basic types; those that contain a microchip and those that do not. There is a radical difference in cost and performance between these two types; to such an extent, in fact, that they rarely compete with one another as to the appropriate type of use. As a general rule, chip tags cost more but have a larger data capacity than chipless tags. Chip tags, for example, are usually not available below a unit cost of about one dollar each when ordered in a quantity of less than one million; whereas many chipless tags are projected to cost less than 20 cents each, even when ordered in quantities as small as one hundred thousand.
Most RFID tags will have a longer reliable range than magnetic strips and bar codes. As a rule, RFID tags can be interrogated without having as significant line-of-sight and orientation problems as are evidenced by bar codes and magnetic strips. Although chip tags do have a longer range than magnetic strip and bar code systems, the range at which they can be reliably used is still a limiting factor.
Chip tags are by far the most popular of the two types of RFID tags. A chip tag consists of four elements or features: (1) a computer microchip; (2) circuits for converting radio signals to computer data signals and back to radio signals; (3) an antenna; and (4) a means for providing DC power to the chip circuitry. In low cost RFID chip tags the first two features are often partially or totally integrated into a single microchip, which integration requires certain compromises in tag performance (read range, number of bits, etc.). This combination of features also leads to certain integrated circuit (IC) cost and/or design compromises to accommodate both digital and radio frequency circuitry on a single IC. The impact of these design compromises can be partially compensated for by use of low radio frequency (RF) operating frequencies that, in turn, lead to rather large and expensive antennas.
The most daunting problem with chip tags is the need for DC power for the chip circuitry. The combination of environmental issues coupled with severe constraints on cost, size and weight usually require that the tag not have a battery or other on-board power source. The only generally useable solution is to obtain DC power by converting RF power received from the tag reader signal into DC power within the tag. Those skilled in the pertinent art term tags without a battery or other power source as “passive” tags, while those that contain a battery or other source are termed “active” tags. The passive method of providing DC power to a chip tag requires a more efficient tag antenna (i.e., larger size and cost) and higher transmitted power levels from the reader. It also requires added components that either add to the cost of the microchip or to the cost of the tag, which additional components also result in an increased tag size. The most important limitation of passive powered chip tags is the severe restriction on the read range of the tag because a signal that is sufficiently strong enough to power the tag will only extend a short distance from the tag reader antenna. Thus, while chip tags have the dominate share of the RFID market, their high cost and limited read range combine to prevent them from replacing either bar codes or magnetic strips in any significant manner.
“Chipless” RFID tags do not contain a microchip but, instead, rely on magnetic materials or transistorless thin film circuits to store data. A major advantage of chipless RFID tags is their relatively low cost. The disadvantages of chipless tags include that they are range limited (several centimeters at the most) and only contain limited amounts of information. The severity of these problems has prevented market acceptance of chipless tags in spite of their low cost potential.
In the year 2000, the global market for conventional RFID systems and services was in the order of 500 million U.S. dollars. This market was largely for chip tags that typically cost from about one dollar to tens of dollars each. While chipless tags are not selling well, they have generated great interest from a number of potential users because of their low cost potential. A huge gap exists in the automatic identification market between the very low cost bar codes and the higher performing RFID chip tags. The overall market is clamoring for a technical solution to fill that gap.
The critical characteristics of any new automatic identification technology that will fill this gap are: (1) a cost of between one cent and ten cents per tag when manufactured in large quantities; (2) reliable reading without the need for manual scanning by a human operator; (3) reliable reading without requiring a line of sight between the tag and tag reader (i.e., reliable reading even if the tag is scratched, or covered with dirt, or on the wrong side of the package, etc.); (4) a reliable read range of at least one to two meters; and (5) a tag data capacity of roughly 100 bits. Such tags are of vital interest to postal authorities, airlines and airports, mass transit authorities, animal breeders, the livestock industry, delivery businesses, any business with significant supply chains, particularly those that maintain inventory or handle fast moving consumer goods, and so on. These are all applications where a high priced tag is not practicable, particularly where the tag is disposable or is going to be sold with the product.
The limitations and problems with prior art identification systems has been the major factor limiting their widespread usage. Although prior art identification systems are frequently associated with computers and computer networks, there has been a very limited demand for access to identification information provided by such prior art devices. In short, the distribution and use of such identification information is limited by the limitations inherent in the devices. What has been needed in the art is a reliable, economically priced, small identification tag upon which can be encoded substantial identification data that can be read at an adequate range and that can be used in a variety of environments and for a variety of applications. As will be discussed herein, such devices and readers for such devices have been recently developed and will soon be available. These identification tags can be encoded with substantial identification data and can be read at an adequate range for use in a variety of environments and for a variety of applications.
Because such identification tags can be used to identify with global certainty a very large number of objects, a system to provide widespread access to the data and other information made possible by such tags is necessary. The volume of information and data made possible by this new identification technology makes the Internet, as currently structured, of marginal usefulness because of the slow speed at which the Internet can be accessed to secure pertinent information.
Therefore what is needed in the art is an object-naming computer network infrastructure for identification tags and a method of operating the same.